1. Field of the Invention
The present invention relates to a system for detecting the shape of an endoscope inserted into a lumen using source coils and sense coils.
2. Description of the Related Art
In recent years, endoscopes have been widely used in the fields of medicine and industry alike. Endoscopes with a soft insertion unit may be inserted into a tortuous body cavity and thus make it possible to diagnose an organ located in a deep region in a body cavity without the necessity of incision. Moreover, the endoscopes with a soft insertion unit sometimes have, if necessary, a treatment appliance inserted into a channel and thus make it possible to conduct therapeutic treatments including resection of a polyp or the like.
The lumen in a body cavity such as a large intestine or small intestine, is tortuous. It is hard for an operator to see at what position the inserted insertion unit of an endoscope is located or in what form the insertion unit is inserted.
In this case, for example, when the lumen of the inferior alimentary track is examined by inserting the insertion unit through the anus, some expertise is needed for inserting the insertion unit into the tortuous lumen.
During insertion, for smoother insertion, a bendable part of the insertion unit must be bent in conformity with the curve of the lumen. The procedure would be more convenient if the position in a body cavity or if the current bent state of the insertion unit could be understood.
In the past, X rays have been irradiated externally to a subject, into which the insertion unit of an endoscope is inserted, in order to detect an inserted state. The inserted state means a position in a lumen, at which the insertion unit is located, or an inserted form of the insertion unit. However, X rays are harmful to a human body. Besides, a place of irradiation in which X rays are irradiated is limited. Thus, X rays are not a preferable means for detecting the inserted state of the insertion unit of an endoscope.
Various endoscopes and apparatuses have been proposed for detecting the inserted state of an insertion unit of an endoscope in a lumen in a body cavity or the inserted state of a catheter thereof by utilizing magnetic fields without a physiologically adverse effect upon a human body.
However, a technology for indicating the positional relationship of an endoscope to the exterior of a body cavity has not been disclosed. Since the positional relationship between the endoscope and the exterior of the body cavity is unknown, into what region in a patient""s body the insertion unit of the endoscope has been inserted cannot be ascertained or in what direction the insertion unit should be inserted cannot be determined. Moreover, since the positional relationship between the insertion unit of the endoscope and an operator""s hand is unknown, what region should be compressed manually cannot be determined.
Additionally, a conventional CRT generally adopted as a monitor deflects an electron beam using magnetic fields and therefore generates unwanted magnetic fields. Assuming that the CRT is used as an observation monitor for displaying an endoscopic image or a shape depiction monitor for depicting the shape of an endoscope for a conventional endoscope shape detection system employing magnetic fields, a magnetic detection device detects magnetic fields generated by a magnetic generation device while being affected by the unwanted magnetic fields generated by the CRT. This poses a problem in that the shape of the endoscope cannot be depicted on a stable basis.
According to a conventional display method implemented in a detection system for ascertaining the shape of an endoscope when inserted, if a patient changes his/her position, the positions and angles determining the shape of an endoscope are changed. Consequently, the user would have to re-set his/her line of sight. Moreover, the shape of the entire endoscope is depicted on the display screen, including regions in which the user is not interested, for example, the exterior of a patient""s body. The user has to therefore distinguish a region which the user wants to scrutinize, for example, an intracorporeal region of a patient, on the display screen.
According to the display method implemented in the conventional inserted state detection system, an estimated shape of an endoscope is depicted with a reference point in a space of detection aligned with the center of the display area on the monitor. A user must modify the setting of a magnification whenever the user finds it necessary. Showing the shape of an endoscope enlarged is known.
However, although an image showing the shape of an endoscope is not displayed in the center of the display area, if the image of the shape is enlarged, part of the image of the shape comes out of the display area. It is impossible to enlarge the image by making the most of the display area. Even when the image of the shape is enlarged and displayed in an easy-to-see manner, the position of the endoscope changes from one patient to another patient. Consequently, the position of the image of the shape of an endoscope differs and part of the image comes out of the display area. This causes a user to re-set a magnification of the displayed image.
When the insertion unit of an endoscope is inserted into the large intestine or the like, the insertion unit may loop spirally. The insertion of the looping insertion unit pains a patient. Whether an operator recognizes the looping depends conventionally on the operator""s skill. This leads to a drawback when looping cannot be recognized readily.
Assuming that the insertion unit of an electronic endoscope is inserted into a body cavity, that a region to be observed is imaged, and that an endoscopic image is viewed through a monitor, it is a matter of common practice that endoscopic images are frozen to produce a still picture which is recorded and viewed for diagnosis. When an image to be frozen appears, a Freeze switch located on an operation unit is pressed. Thus, data of a desired image is recorded in a frame memory or the like in a video processor and then output to the monitor or the like. Eventually, a still picture is displayed.
However, when the Freeze switch is pressed, if the distal part of the insertion unit in which an imaging device is incorporated moves, a color mismatch will be observed in a still picture.
With conventional inserted state detection systems, a user converts images of the shape of an endoscope, which are displayed in the form of a motion picture, into a video signal. The images are then recorded on a video tape for future use in diagnosis or analysis succeeding an examination. The same picture as that viewed during the examination only can be reproduced from the recorded video tape. It is impossible to observe the shape of the endoscope in different directions.
When a conventional endoscope shape detection system is employed, extracorporeal markers are used to mark specified positions on the body surface of a patient for a better understanding of the positional relationship between an endoscope and the patient body. An operator or paramedic must manually affix the extracorporeal markers to the specified positions on the body surface, or fasten them using a tape or the like. The specified positions on the body surface serve as reference positions, for example, such as a position near the anus.
However, according to the foregoing fastening method, if the extracorporeal markers are removed to allow the patient to change his/her position, it is hard to place the markers at the same positions.
An object of the present invention is to provide an endoscope shape detection system making it possible to readily grasp the positional relationship between the shape of an insertion unit of an endoscope and the exterior of a body cavity.
Another object of the present invention is to provide an endoscope shape detection system capable of suppressing the adverse effect of unwanted magnetic fields generated by a monitor, and depicting the shape of an endoscope in a more stable manner.
Still another object of the present invention is to provide an endoscope shape detection system making it possible to view the shape of an endoscope with a line of sight set in an easy-to-see direction while being unaffected by a change in a patient""s position.
Still another object of the present invention is to provide an endoscope shape detection system capable of depicting the shape of an endoscope without causing part of the shape to come out of a display area. Specifically, when the shape of an endoscope is depicted at a size permitting a user to find depiction easy-to-see, even if a subject is changed to another having a different size, no part of the shape will come out of the display area.
Yet another object of the present invention is to provide an endoscope shape detection system making it possible to recognize the looping of an insertion unit, as it is being inserted, in the course of detecting the shape of an endoscope.
Yet another object of the present invention is to provide an endoscope shape detection system capable of producing a desired still picture by freezing images according to a motion made by an insertion unit.
Yet another object of the present invention is to provide an endoscope shape detection system making it possible to observe the shape of an endoscope in an easy-to-see manner all the time even during diagnosis or analysis succeeding an examination.
Yet another object of the present invention is to provide an extracorporeal marker fastening device for an endoscope shape detection system. The extracorporeal marker fastening device makes it possible to set extracorporeal markers at the same positions even when they had to be removed to allow a patient to change his/her position.
An endoscope shape detection system in accordance with the present invention consists mainly of a first coil means, a second coil means, a third coil means, a transmitting and receiving means, and an arithmetic means. The first coil means is inserted into a subject. The second coil means is located at a predetermined position. The third coil means can be located at any position on the subject. The transmitting and receiving means permits transmission and reception of a first magnetic signal between the first coil means and second coil means, and transmission and reception of a second magnetic signal between the third coil means and second coil means. The arithmetic means calculates first position information corresponding to the position of the first coil means relative to the second coil means according to a first detection signal resulting from transmission and reception of the first magnetic signal. The arithmetic means calculates second position information corresponding to the position of the third coil means relative to the second coil means according to a second detection signal resulting from transmission and reception of the second magnetic signal.
In the endoscope shape detection system of the present invention, the arithmetic means calculates the first position information corresponding to the position of the first coil means relative to the second coil means according to the first detection signal resulting from transmission and reception of the first magnetic signal. The arithmetic means also calculates the second position information corresponding to the position of the third coil means relative to the second coil means according to the second detection signal resulting from transmission and reception of the second magnetic signal. Consequently, the endoscope shape detection system makes it possible to readily grasp the positional relationship between the shape of the insertion unit of an endoscope and the exterior of a body cavity.
Other features and advantages of the present invention will become apparent from the description made below.